A surface maintenance machine having a debris hopper that can be dumped in either a street level position or a high lift position.
In U.S. Pat. No. 3,312,992 there is disclosed a street sweeper having a hopper that can be dumped in either a street level or a high dump position, hooks being provided on the lift arms that release their latching engagement with the hopper doors lugs as the hopper is pivoted to a dumping position. However with such structure the lower edge of the discharge door is at a substantial higher elevation than the hopper bottom wall which results in the hopper having to be turned through a relatively large angle to be completely emptied. Additionally to prevent debris in the hopper moving toward the debris inlet as the hopper is being elevated, the control for the dump cylinder also has to be operated. This can result in the door being released to open prior to the hopper being moved to its maximum elevated position.
It is old to provide automatic latch release mechanism for discharge gates on dump trucks, see for example U.S. Pat. Nos. 1,495,385 and 2,437,890. However such mechanism is not suitable for hoppers mounted on lift arms of sweepers wherein the hopper is pivoted relative the arms as the hopper is moved to a substantially elevated position and it is desired to maintain the discharge door latched while pivoting the hopper so debris does not slide toward the end of the hopper opposite the discharge door.
In order to provide improved mechanism for elevating a hopper of a surface maintenance machine and retaining the discharge door in a latched condition until the hopper is to be dumped and automatically release the latch as the hopper is pivoted to a dumping position, this invention has been made.